Wednesday, February 11, 2009

From Adamas to Bort

The word diamond comes from the ancient Greek word "adamas" which means "unbreakable, that cannot be tamed". Since its discovery thousands of years ago, diamonds had already lived up to its name as they are considered to be one of the hardest known naturally occurring minerals in the world. The hardness quality of the diamond makes it also an important mineral in industrial applications in addition to its use in jewelry.

Diamond is a material renowned for its unparalleled physical qualities. Because of this, the only material that can scratch a diamond is another diamond. A polished diamond can last a long time and would not be scratched unless it is rubbed against another diamond. The best industrial-strength abrasives were made with diamond dust.

In the industry sector, diamonds of high dispersion index, extreme hardness, and extremely high thermal conductivity with a 900-2320 W/m K are most useful. These properties are the factors that make a diamond exceptionally worthy in industrial applications, it is an ideal material for grinding and cutting tools. Diamonds that are commonly used in industry are the less expensive ones. These include the flawed, the colored, and the unclear diamonds. These industrial-grade diamonds are commonly known as bort.

Thursday, February 5, 2009

Jewel Identification and Theft

Because each gemstone is unique when considered with all its variables (cut, color, irregularities, inclusions, refraction, reflection) it is possible to photograph a particular stone and record its measurements and ratings to establish a unique fingerprint that will identify that stone as surely as a serial number.

This procedure is now being carried out on certain stones by certain insurance companies and individuals. The cost factor is prevalent.

Even if a stone is "fingerprinted" and then stolen, there is no centralized source location that every buyer or even every jeweler or gemologist will check before purchasing the stone. This record comes into play more often when a stone is recovered and ownership is in question.

There are some exceptions to this rule. Stones that are of immense value or highly individualistic are put on hot lists. Organizations such as Interpol keep a record and submit copies of printed information along with any suspects' names to various countries' police agencies, and a group called the Jeweler's Security Association puts out bulletins and occasionally flashes to their various members on particularly bold, large or unusual gem thefts.

The criminal counter to this type of record keeping is to immediately remove any stones from their mountings and melt the mountings down for the precious metal they contain. The stone is then sold individually or mixed in with a group of other non-illegal stones and sold in a grouping. As anyone knows, if the stone is held a while, the "hotness" becomes less of a factor in a sale.

Large, unusual or famous stones can be taken to a less than honest cutter, who can cut the stone down into a number of smaller stones. This naturally wastes some of the material as does any cutting procedure and makes the stones intrinsically less valuable as size is a coveted asset in investment quality (or even jewelry quality) gemstones.

In spite of identification and insurance company efforts, jewels still remain one of the most highly sought after targets and any jeweler or diamond cutter realizes he must constantly update his security precautions and it is still probably only a matter of time before he is hit. Insurance rates for these people are fairly substantial as one would imagine.

Tuesday, February 3, 2009

Refining Rubies

There are a number of ways to treat rubies to improve their color, clarity and ultimately, their value. The quick fix method is to dye or oil the ruby which will help hide fractures, inclusions and improve the color of the stone.

A further refinement of this is a diffusion process where stones are immersed in a chemical bath which contains a number of chemicals including chromium which gives the ruby its color in the first place. This color is carried in the skin of the ruby by the chemicals and actually penetrates the skin. This generally produces a light tone and the tone is only a skin which will disappear upon re-polishing.

The next common treatment is a heat treatment. Rubies stand heat far better than emeralds do and it is fairly common to heat both rubies and sapphires which tends to improve the color by driving out bluish or brownish tints and will tend to dissolve the transparency, lessening the "silk" inclusions on heavily included stones.

These treatments all are dependent upon temperature, time and cooling rate, but they will bring about a permanent change in the stone leaving no chemicals or treatment to be removed.

In top ratings, rubies are rarer than diamonds but the actual supply of top stones may vary greatly because of political situations. Many stones reach the world markets because they have been smuggled out of places (especially Burma) through Thailand and other friendlier countries. There is a fair amount of profit to be made in the smuggling of rubies.

Smaller, included or industrial strength stones, are cheaper than their diamond cousins because they are more easily available.

The rhodolite garnet often approaches ruby in color, although tends to be more purplish than the ruby and less saturated but still are sometimes sold as rubies.

Tourmaline also occurs in many color ranges including red ruby and is sometimes sold as ruby.

A new stone called red spinel has a remarkable resemblance to ruby and is not often seen on the market because it is generally sold as a ruby.

Rubies have been synthesized since the late 1800s. There are two primary methods of synthesizing rubies - the fusion method and the pulling method. In the 1950s, several manufacturers began flux growing rubies which takes considerably longer than the other methods and produces a stone much closer to its natural version.  Flux grown rubies tend to be extremely clear and transparent with an orange overtone.

Fusion stones tend to be strikingly flawless looking while the flux methods may actually produce a number of inclusions resembling silk.

One clue to synthetic rubies is the cut. Because the material is cheaper and waste is not as much a problem, machine cuts such as square or rectangular cuts are more prevalent.